1. Field of the Invention
The present invention relates generally to a TV lens system, particularly to a TV lens system which can change characteristics with respect to control of positions or moving speed of a focus lens and a zoom lens of a TV lens apparatus.
2. Description of Related Art
In a TV lens system used for a TV camera, lenses such as a focus lens and a zoom lens, which are driven by a motor, are controlled in accordance with control signals outputted from lens controllers for focus and for zoom. Typically, the zoom lens is controlled with its moving speed in accordance with the control signal outputted from the zoom controller, and the focus lens is controlled with its position in accordance with the control signal outputted from the focus controller.
A conventional TV lens system is known in which an operator can select, by using a selecting means such as a switch, a desirable output characteristic of the zoom controller from output characteristics of a plurality of types that are prepared beforehand. The output characteristic of the zoom controller describes an electric voltage of the control signal outputted from the zoom controller with respect to an operational amount of an operating member (e.g. a thumb ring) provided to the zoom controller. If the output characteristic is changed, the response characteristic of a moving speed of the zoom lens with respect to the operational amount of the operating member is changed. The operator can select, depending on demands, a setting of a control characteristic; for example, an operatability of the zoom controller in a low speed range of the zoom lens takes priority to be better than other speed ranges. Japanese patent No. 2810437 recites a TV lens system that can change the response characteristic of the speed control of the controlled member with respect to the operational amount of the operating member in a speed control apparatus for controlling the speeds of the controlled members, in accordance with the operational amount of the operating member, such as controlling the speeds of the controlled members.
However, in a conventional art, in a case to switch the output characteristics of the zoom controller, one characteristic must be selected from the output characteristics of the types that are determined beforehand. Thus, a number of types of the output characteristics to be selected by the operator are limited. Moreover, when increasing types of the output characteristics that can be selected, corresponding numbers of switching means and a memory capacity are required; hence, the numbers are limited. If there are too many types of characteristics, the operator has difficulties in memorizing contents of the output characteristics of various types, and the system becomes inconvenient as a result.
It is more useful if the operator can change the characteristics depending on demands, not only the output characteristics of the zoom controller, but also the characteristics related to control of the optical members (e.g., a zoom lens, a focus lens, an iris, and an extender) that are driven with motors in a TV lens apparatus, such as the output characteristic of the focus controller or a deceleration curve in the proximity of the mechanical stopping end of the zoom lens. However, the same difficulties are caused as the case described above if the characteristics are changeable.